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1.
When something is more almost than another something.
Oh well it's almost St-Patties Day, but it's almoster Friday!
by Guillaume 3D March 09, 2009
 
2.
Someone who wines and dines girls in the attempt of sleeping with them but frequently comes up short.-only to describe the events as an almost success.
Phil: hey how'd things go with christy last night?
Sean: I almost fucked her.
Phil: ahh you suck, youre such an almoster.
by laurence of alaybia February 27, 2011